With the rapid development of the low-altitude economy， the scale of low-altitude aircraft operations continues to expand， and the demand for efficient and reliable communication networks is becoming increasingly urgent. Current communication technologies fail to meet the stringent demands of low-altitude applications in terms of wide-area coverage， high-mobility support， and diverse service provisioning. This stark disparity necessitates the development of a novel， dedicated network architecture. This paper begins by elucidating the technical background and unique challenges inherent to low-altitude communication， addressing critical issues such as the modeling of high-dynamic complex channels， three-dimensional mobility management， intelligent sensing for obstacle avoidance， quality-of-service assurance for heterogeneous services， and efficient spectrum utilization. Subsequently， this paper provides a systematic exposition from two dimensions： The evolution of network architectures and the development of key technologies for low-altitude communication. It delves into the principles and state-of-the-art of core solutions， including space-air-ground-integrated networking， intelligent beamforming， and dynamic resource management. Finally， this paper outlines promising research directions， such as integrated sensing and communication （ISAC） as well as native intelligence and security， with the aim of offering a theoretical foundation and technical insights for constructing next-generation low-altitude communication networks.